Decorative trim strip assemblies have been applied to vehicles, particularly automobiles, vans and the like, for a great many years. Such trim strips have been in the form of side moldings or edgings, for both decorative and protective purposes. Usually such trim strips as body moldings and the like are formed of an extruded polyvinyl chloride or other polymeric resinous material; and they may have their outer surface covered or embossed, or a combination thereof, so as to give a particular desired decorative appearance and surface contour. For example, they may be covered with a pre-printed plastic film having such as a wood grain effect, or a metallized film such as polyethylene teraphthalate which gives the outer surface of the trim strip a metallic--usually a bright metallic--appearance. Such trim strips have generally been bonded to the surface to which they are mounted by way of an adhesive backing, and are sufficiently pliable as to adapt to the contour of the surface to which they are applied.
However, it has been the trend in vehicle design to use relatively broad or wide protective and/or decorative trim strips to define certain areas on the vehicle surface, both inside and outside the vehicle such as on doors, interior door panels, dashboards, and the like. Particularly, it has been the trend to make designs embodying wide trim strips having laterally curved portions in them, where the curve is substantially in the plane which defines the width of the trim strip.
Moreover, due to the nature of the design of such laterally curved trim strips, and their placement on or in a vehicle, it is possible that they may be secured to a rigid backing plate of sheet steel or the like, so as to secure them in place and to assure that they maintain their curved appearance and do not tend to straighten themselves by bending laterally away from the direction of the curve.
However, bending trim strips as aforementioned can create severe compressive and tensile stresses in the material of the trim strip, particularly the plastic material, on the inside and outside respectively of the neutral axis of the trim strip with respect to the direction of lateral curvature. If these stresses are excessive, the appearance of the laterally curved trim strips is affected, and they may be crazed, stretch marked, wrinkled or corrugated, or the covering film or material may be torn.
One attempt to overcome the above problems has been to cast the portion of the decorative trim strip which is laterally curved, and then to assemble it with conventional extruded trim strip having the same general, appearance in an appropriate manner according to the vehicle assembly procedures. However, it may very often happen that the cast portion has a different appearance, colour or contour than the remaining extruded portions; and in any event, it is comparatively very expensive since it requires the preparation of injection molding dies and the use of additional molding equipment.
One particular attempt to solve the above problems has been proposed by Loew in Canadian Pat. No. 1,020,199, issued Nov. 1, 1977. What Loew has done is to provide a plurality of strips of polymeric resinous material which are fitted side by side in the curved portion of a composite decorative trim strip. The various longitudinal strips may have differing widths, and each individual strip is stressed to an extent that does not exceed the stress resistance of the material of the respective strip. [The term "stress resistance" is defined hereafter.] All of the strips are bonded in a side-by-side fashion to a supporting substrate.
However, the cost of handling, and extruding separate longitudinal polymeric strips, and assembling them one at a time, can become excessive; and may require some compromise in the design and appearance of the outer surface of the strip, so that the abutting edges of the various individual strips are not highly visible. Moreover, Loew generally calls for overlapped relationship of adjacent strips in the composite decorative trim strip, which requires assembly in the correct order, so that the handling and general labour costs in producing each formed composite decorative trim strip having a lateral curvature may become quite high. "Stress resistance" of a longitudinal trim strip or a longitudinal portion of a trim strip is defined as being the limit or ability to which the plastic trim strip may be laterally bent in a curvature such that the compressive and tensile forces set up on the inside and outside, respectively, of the neutral axis in that strip do not cause an apparent visible surface aberration or failure. Such surface failure may, as noted above, include crazing, tearing, stretch marking, wrinkling or corrugating, any of which is undesirable and is usually unacceptable when present in a laterally curved decorative trim strip of the sort contemplated herein.